1. Field
The described technology generally relates to an organic light-emitting display apparatus, and more particularly, to an organic light-emitting display apparatus having low driving voltage and improved image quality and lifetime.
2. Description of the Related Technology
Portable thin flat panel display apparatuses have been used as a replacement for display apparatuses. An organic or inorganic light-emitting display apparatus, a type of thin flat panel display apparatus, is a self-emission display apparatus. The organic or inorganic light-emitting display apparatus may have a wide view angle, excellent contrast, and quick response speeds. Also, an organic light-emitting display apparatus, in which a light emitting layer is formed of an organic material, may have excellent luminance, driving voltage, and response speed, as compared to an inorganic light-emitting display apparatus. Additionally, an organic light-emitting display apparatus may display multi-colors.
In an organic light-emitting display apparatus, an organic emission layer may be interposed between a cathode and an anode, and, when a voltage is applied to the cathode and the anode, the organic emission layer connected to the cathode and the anode emits visible light.
The organic emission layer may include an organic emission layer emitting different colors of visible light such as red, green, or blue. In the organic emission layer, holes and electrons are recombined, thereby emitting visible light. However, surplus electrons that do not participate in the recombination move toward a hole injection layer (HIL), a hole transport layer (HTL) or a first electrode, thereby resulting in deterioration of light efficiency and life of an organic light-emitting display apparatus.
In particular, in a structure in which a blue organic emission layer is commonly used in all sub-pixels, the surplus electrons generate visible light in a different organic emission layer, and thus color mixture occurs, thereby resulting in deterioration of image quality. Therefore, difficulty exists when trying to improve the image quality.
An organic emission layer may be directly patterned to different thicknesses by laser induced thermal imaging (LITI). In detail, a donor film including a light-to-heat conversion layer (LTHC) and a transfer layer is aligned on an organic emission layer as a receptor and attached thereto, and laser beams then irradiate the donor film, thereby completing the patterning process. When the organic emission layer is formed by LITI, the formation of the organic emission layer does not require a separate chemical treatment process and thus the organic emission layer is not damaged and manufacturing processes are simplified as compared to the photolithography method. However, in a transfer mechanism, only a donor film is not transferred by laser irradiation and the laser beams need to be irradiated up to portions disposed below the donor film to perform the transfer process. Thus, if the thickness of organic emission layer to be substantially transferred increases, more energy necessary for the donor film through layers deposited below the donor film and on a substrate is consumed. Such an excessive energy may incur thermal degradation of organic materials constituting the organic emission layer, thereby deteriorating the characteristics of an organic light-emitting device.